Graphs are important for supporting critical thinking and scientific argumentation because students can use them to reason, make judgments and decisions, and solve problems like a scientist (Connery 2007). Yet teaching students how to use math to actually think critically continues to be difficult for teachers. This article describes two activities that teach students how to make a scientific argument and articulate a scientific claim (Driver, Newton, and Osborne 2000). First is a math activity that uses lemonade to teach students reasoning skills with graphs; the second is a science activity with a basketball and pump that uses a discrepant event to make a claim about the nature of air. (Contains 3 figures.)